A telescopic sight is known from the related art which is composed of an objective, an ocular, and a reversal system. The telescopic sight has a variable magnification, so that objects may be observed magnified. For example, reference is made to DE 102 58 733 A1 in this regard, from which such a telescopic sight is known.
The objective of a telescopic sight of this type is typically achromatically corrected. The vertex image distances for red and blue light are thus equally long, but the vertex image distances for green light deviate. This deviation is typically referred to as a longitudinal chromatic aberration or also as a secondary spectrum. The secondary spectrum of the objective of a telescopic sight of this type often results in color fringes at light-dark transitions. These are often very annoying to an observer who observes an object using the telescopic sight. This interference is all the more obvious the greater a magnification of the object is selected on the telescopic sight.
An achromatic lens system is known from U.S. Pat. No. 6,226,132 B1, in which the secondary spectrum may be decreased by selecting a suitable deviating relative partial dispersion. However, the relative aperture of this known lens system is 1:10. But such a relative aperture is inadequate for telescopic sights.
Accordingly, it would be desirable to provide an optical system in which the secondary spectrum is decreased and whose relative aperture is sufficient so that the optical system is usable in a telescopic sight.